1. Field of the Invention
This invention relates to an automatic sheet feeding device, and more particularly, to a sheet-material feeding device for feeding a sheet material to a predetermined position such as an image reading position or the like, for use in an image forming apparatus, such as a copier, a laser-beam printer, or the like.
2. Description of the Related Art
A conventional automatic sheet feeding device is provided at an upper portion of an image forming apparatus. The original sheets are mounted on a sheet mount and then sequentially fed from the lowermost sheet of the stack by a feeding roller. Thereafter, each fed sheet is detected by a sheet detector provided downstream of the feeding roller. When the fed sheet does not reach the sheet detector within a predetermined time period, the lowermost sheet is pressed against the feeding roller by operation of a sheet pressing member (also called a weight), whereby the feeding force of the feeding roller is increased to assist in the sheet feeding operation.
In the above-described conventional device, each time a failure is detected during the feeding operation of an original sheet from among the original stack, a sheet feeding operation is performed by operating the sheet pressing member after the lapse of a predetermined period of time. Hence, the time required for feeding the entire stack of originals to an image reading position on the image forming apparatus increases, thereby greatly increasing the processing time of the image forming apparatus.